This invention relates to a treating apparatus utilized for pre-treatment process in which workpieces such as car bodies, household electrical goods or steel furniture are treated with degreasing, water washing and chemical conversion coating, or utilized for washing process in electrodeposition treatment.
In general, metallic workpieces to be treated are processed through a series of treating stages comprising degreasing, water washing, chemical conversion coating, water washing and painting. The term "pre-treatment" used herein means a treatment process before the painting stage.
In conventional treating apparatus, workpieces to be treated are transferred through several stages in succession by a conveyor. For example, a pre-treatment for painting a car body is carried out through the aforementioned stages, in which the car body is sprayed with chemical liquid or immersed into a dipping bath. Since workpieces are generally formed in complicated shapes, cavities behind the workpiece or inside surfaces thereof are apt to remain untreated due to blind spaces or floating bubbles, resulting in poor painting.
To eliminate the above difficulties in the way of performing high quality painting, many attempts have been made. In a most popular design, a travelling workpiece is supported by a pair of hoists through vertically extending wires. When the workpiece is immersed into a dipping bath, the hoists actuate in cooperation, simultaneously or alternately, to move the workpiece piece downward allowing it to swing or oscillate for expelling air bubbles from inside thereof. Since the workpiece is suspended through longitudinal wires, it is apt to oscillate in lateral directions while it is immersed into the bath. To prevent the workpiece from colliding against the wall of the tank, the vertically extending wires should be operated slowly. As a result, it is impossible to accellate the treating speed of the workpiece.
In another prior design, a tilting cylinder is mounted near a bottom end of a vertical elevator post such that a lifting rest for a workpiece can be oscillated in lateral directions. In this design, however, the workpiece is oscillated relatively distant from the central position, so that the dipping bath needs a larger width as well as a greater quantity of treating liquid.